Microscopicdings in the trachea and bronchi in 90 cases of influenza studied by Askanazy1 revealed hyperemia and minimal cellular infiltrate as the earliest alteration. These were followed by intensification of hyperemia, edema, occasional necrosis, and desquamation of the surface epithelium. The next stage was accompanied by simple or fibrinoid necrosis, often in conjunction with alterations that Askanazy referred to as squamous metaplasia. These findings were more pronounced in the bronchi than in the trachea.
Winternitz2 likewise found histologic alterations to be more severe in the distal bronchial system than in the trachea. Loss of cytoplasmic granularity and increased nucleus staining were the earliest changes noted to accompany the usual intense hyperemia, edema, and exudation. Both Askanazy and Winternitz felt that acute, massive necrosis of tracheal, bronchial, and bronchiolar epithelium were the characteristic lesions of influenza and were not to be found in any other type of acute pulmonary
BRONCHOTRACHEAL RESPONSE IN HUMAN INFLUENZA. JAMA. 1961;178(13):1191. doi:10.1001/jama.1961.03040520023005